Toxicity of heavy metals and insecticides on the slime mold Physarum polycephalum was investigated in order to examine and estimate with ease the toxicity of environmental and occupational contaminants and also to study the effects of various agents on the cell membrane. Changes in survival time and in membrane potential of the slime mold were measured using a double chamber method. The results obtained suggest that their toxicity for the slime mold is accompanied by some change in the cell membrane, and that studies on toxicity for various chemical substances in the slime mold can be used as a screening method.
Effects of single exposure to toluene on Sidman avoidance response in rats were studied. The animals, in which the behavioral base line had been established, were exposed 0, 1, 000 and 3, 000ppm of toluene vapor for 4 hours and the effects on the behavioral pattern were investigated using Sidman avoidance test for one hour after the termination of toluene exposure. 1) Exposure to 0 or 1, 000 ppm of toluene did not produce marked change on the operant behavior. After the exposure to 3, 000 ppm, the animals produced increased responses with shortening of the inter-response-time (IRT) and no changes in shock counts from the beginning to the 50min. zone of the Sidman avoidance test when compared with those before exposure. The behavioral change indicated here appears to be caused by a temporary breakdown of the established timing of lever pressing. 2) The effect of toluene on the operant behavior was strongest immediately after the termination of the exposure and the behavior recovered in about an hour. This result suggested that toluene is rapidly transfered to and removed from the brain.
A possible mechanism of infertility by Cd was investigated from the standpoint of influence of Cd on the contractile responses of isolated seminal vesicle from guinea pigs to K, acetylcholine, noradrenaline, Ba and Ca by using the Magnus method. Cd inhibited the contractile responses to the contractile agents tested in a dose-dependent manner. Cd showed the preferential inhibition against the contractile responses to K and Ca. The inhibitory effect of Cd on the contractile responses to noradrenaline and acetylcholine was hardly removed. The effect of Cd was inhibited by the thiol compounds, glutathione and thiola. The active mechanism of Cd was discussed in relation to Ca mobilization.
Acute thallotoxicosis has been studied in an autopsy case with characteristic neurological symptoms. Pathologic findings were composed of a rarefaction in cerebral white matter, swelling and fragmentation in peripheral nerve fibers and some chromatolytic changes in neurons of cranial nerves and spinal cord. Trace amounts of thallous salt were measured in the tissues from the brain, liver and kidney using spectrophotometric technique. The locus of thallium affection is assumed to be a mitochondrial membrane with a specific affinity to the thallous ion.
A single or repeated administration of trichothecene mycotoxins to mice induced leukocytosis and leukopenia. Acute and sub-acute toxicosis of trichothecenes was characterized by hematological and pathological observations.
Pipemidic acid (PPA) orally given in a dose of 100 mg/kg/day or more was found to cause lame gait in immature beagle dogs of about 3 months old. Their diarthrodial joints were abnormal with increased synovial fluid and blister formation under the outer layer of the articular cartilage. However, such an abnormality was not found in dogs younger than 2 weeks or older than 12 months. The blisters were formed at the joint areas bearing the body weight at a time when PPA was considered to be present there. Nalidixic and piromidic acids, structural analogues of PPA, also caused abnormality similar to PPA. The severity of the arthropathy was slight with piromidic acid as compared with PPA and nalidixic acid. The gait abnormality was almost disappeared spontaneously even if medication was continued. The incidence of the arthropathy was not or rarely observed in any young rats, rabbits and monkeys.